Hard disk drives used for long term magnetic storage of digital information are ubiquitous and essential devices in our modern world. A hard disk drive device includes one or more rotating magnetic storage disks within an enclosure. To use the hard disk drive to store and retrieve digital information, the hard disk drive device also includes electronic and control mechanisms that are adapted to read and write information from and onto the magnetic disk. One of these components, a “head-gimbal assembly,” is part of a suspension assembly that provides electrical connections to a read or write head (“read head” for short). The read head is a component of a “slider” that includes the read head, an air bearing surface, and electrical connections. The suspension assembly typically includes a laminated flexure to carry electrical signals to and from the read head, between the read head and an electronic device such as a computer. The head-gimbal assembly is a component of a head-stack assembly that typically includes multiple head-gimbal assemblies, with each head-gimbal assembly being attached at an end of a suspension arm attached to an actuator.
A read head of a slider includes one or more miniaturized transducers for reading or writing data from or onto the rotating magnetic disk. The slider also includes an air bearing surface to properly position the read head above the disk as the disk rotates. Electronic functionality, including, for example, electrical contact pads and other electrical connections, is also part of the slider The disk includes a magnetic layer that can be selectively magnetized by a write head to store digital information in a manner that allows for retrieval of the information by a read head.
The head-gimbal assembly is attached to an actuator arm (a suspension arm attached to an actuator) that is part of the disk drive, and is held by the actuator arm to place the slider at a location that is adjacent to but not touching a surface of the magnetic disk. As the disk spins, airflow at the spinning disk surface interacts with the air bearing surface of the slider to create a cushion or “bearing” of air flowing through the space that separates the slider from the disk surface. This cushion of air, or “air bearing,” suspends the slider and read head at a desired distance from (“above”) the disk surface. If the read head is too distant from the surface, signal loss will occur, and if the head is too close to the surface the read head could contact the surface, i.e., “crash,” causing damage to the read head or to the disk and often a complete hard drive failure.
Typically, as part of a finished suspension assembly, a slider is permanently bonded to a head-gimbal assembly that is part of a suspension assembly. But before a suspension assembly can be incorporated into a disk drive, the read head of the suspension assembly must be shown to have proper reading and writing capabilities, which requires electronic testing. This type of performance testing is referred to as “dynamic electrical testing” or “DET.”
Dynamic electrical testing can be performed with desired accuracy if the testing conditions closely resemble actual conditions during operation of the read head. For example, the accuracy of the dynamic electrical testing may be improved by holding and electrically connecting the read head using a suspension assembly that is similar to a suspension assembly to which the read head will be bonded as part of a final product. But, if the read head is permanently attached to the suspension assembly during this testing, and then is found to be defective, an entire suspension assembly, including the slider, head-gimbal assembly, and actuator arm, must be discarded.
To avoid discarding an entire suspension assembly due to a defective read head, as determined by electronic testing, a desired approach is to test a read head of a slider without permanently bonding the read head (slider) to a head-gimbal assembly. If the read head is found to be defective by testing carried out before the read head is permanently bonded to a suspension assembly, the read head alone can be discarded or repaired, not the larger and higher value suspension assembly.
Test assemblies that simulate a use condition during dynamic electrical testing have been proposed and used commercially. As with most aspect of manufacturing microelectronic devices such as hard disk drives, test methods and testing assemblies for dynamic electrical testing of hard disk drive sliders must be continuously updated and improved.